Momentum gauge piston stop



Feb. 27, 1951 w. s. SHULTZ 2,543,732

MOMENTUM GAUGE PISTON STOP Filed May 27, 1949 WILLMIW HULTZ W322;

Patented Feb. 27, 1951 oME mUM GAUGE PISTON STOP William S. Shultz, Woods Hole, Mass, assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application May 27, 1949, Serial No. 95.8%

1 Claim.

This invention relates to measuring and testing instruments, and more particularly to a piston construction for momentum gauges utilized in measuring shock waves resulting from the detonation of explosive materials under water.

An object of the invention is to improve the operation of a piston in a cylinder for purposes such as are required in making momentum gauges, and to devise means for controlling the movement of a piston so that it may be prevented from moving other than in one direction. The above and other objects will appear from the following description, taken in conjunction with the accompanying drawing, in which:

Fig. 1 is a view in side elevation of a piston member constructed in accordance with the invention; and

Fig. 2 is a view partly in section and partly broken away, and showing the piston of Fig. 1 in 'an operative position within a portion of a testing instrument. I

In measuring shock waves with momentum gauges, a piston member is caused to move against a copper sphere by reason of the force of an explosion which is being measured under water. The impact of the piston produces a measurable change in the copper sphere which serves as a basis for calculating the magnitude of the explosion. It will be apparent that if the movement of the piston against the copper sphere is repeated accidentally, an erroneous determination may result.

In accordance with the invention, I have constructed an improved momentum gauge piston in which means are provided for preventing the piston from falling back and striking the copper sphere a second time.

Referring more in detail to the drawings, l denotes a piston member such as is commonly employed in momentum gauges. Formed in the side of the piston is a slot l2 which is preferably elongated as shown in Fig. 1, and which has a bottom surface disposed at an angle to the axis of the piston. At its right-hand side, as viewed in Figs. 1 and 2, the slot is relatively shallow so that a ball 14 supported in the slot would project outwardly beyond the periphery of the piston. As the slot extends along the piston, it gradually increases in depth as is more clearly shown in Fig. 2, until the depthof the slot exceeds the diameter of ball l4.

, At one side of the slot 12 is a trip hole l6 communicating with the shallow end of the slot and with the right end surface of the piston, so as to provide means for contacting the ball from v 2 outside of the piston to dislodge the ball from the shallow end of the slot. At the opposite side of the slot, there is formed an opening IS in which is located a spring member 20, as shown in Fig. 2. Numeral 22 denotes a spring steel insert which is mounted at the bottom of the slot.

In operation, the piston moves in a direction from left to right as viewed in Fig. 2, within a test instrument, a portion of which is shown at iii, and during such passage the ball member it assumes a position such as that shown in Fig. 2 in which little interference with the periphery of a cylinder occurs. When movement of the piston stops, however, the spring member 20 urges the ball forwardly into a position in which it projects beyond the peripheral wall of the piston and tends to engage with an adjacent cylinder surface. Any tendency for the piston to move in a direction from right to left, as viewed in the drawings, then causes the ball to jam or lock between the relatively shallow end of the slot and the cylinder wall, thus effectually preventin any movement or dropping back of the piston. When it is desired to release the piston from the locked position, thismay be done by dislodging the ball l4 through the trip hole 16.

By this arrangement it is possible to eliminate any secondary impacts of a mo ntum gauge piston against theelements with ich it coopcrates, for example, a copper sph and a more dependable reading is thus provided for. It may be desired, however, to employ the piston stop construction with other types of gauges and mechanisms where it is desired itemporarily to check movement of a piston in "one direction in the manner common to momentum gauges. Similarly, the'means 'fonlocking the piston may take various formsandfs'hapes, both with respect to the slot, the ball, and the resilient means for urging the ball into the relatively shallow end of the slot. A' plurality of slots and balls could be used, if desired.

While I have shown a preferred embodiment of my invention, it should be understood that various changes and modifications may be resorted to, in keepin with the spirit of the invention as defined in the appended claim.

I claim:

In a testing instrument, a piston having a slot extending longitudinally therein, said slot having a bottom surface disposed at an angle to the axis of the piston, a locking element movably mounted in said slot and dimensioned with relation to the dim hsion of the slot so as to lie wholly within t-h lot when the element is at 4 the deep end of the slot and to extend beyond REFERENCES CITED the peripheral surface of the slot when in the The following references are of record in the shallow end of the slot, and biasing means urgfile of this patent: ing said element toward the shallow end of the slot, said piston having an opening providing 5 UNITED STATES PATENTS communication between the shallow end of the Number Name Date slot and an end surface of the piston to facili- 1,523,290 Rimailho Jan. 13, 1925 tate dislodging of the element from the shallow 2,029,016 Cadmus Jan. 28, 1936 end the FOREIGN PATENTS WILLIAM S. SHULTZ. 10

Number Country Date 23,646 Great Britain NOV. 16, 1905 

